Rectifying process



June 25, 1935. D. E. STINES RECTIFYING PROCESHS Filed Dec. 29, 1931 QN5N QXAN v QM Patented June 25 1935 UNITED STATES PATENT OFFICE- nno'mwmernooass Daniel E. .Stines, Plainfleld, N. 1., aasignor to 7 Standard OilDevelopment Company, a corporation of Delaware Application December 29,1931, Serial No. 583,680 12 Claims. (c1. 196-94) a mutual solution oftwo materials of quite widely difierent boiling points by fractionationso as to obtain one or both of the materials in a substantially purestate as regards contamination by the other material.-

Another object of the invention is to accomplish separation of thematerials while maintaining the quality of each of the materials.

Other objects will be apparent from the specificationand from theaccompanying drawing in which latter the figure is a diagrammaticrepresentation of a preferred apparatus for carrying out the invention.

With a preferred embodiment in mind but without intention to limit theinvention more than is required by the prior art, the raflinate from asolvent extraction treatment of lubricating oil distillate can beseparated into two fractions, namely, substantially pure solvent and asubstantially solvent-free petroleum fraction. Such a railinate consistsof approximately 10 percent of the solvent, which may be a pure compoundboiling at 300 F., and 90 percent of a petroleum fraction having aninitial boiling point of approximately 800 F. It is desired to recoverthe solvent at least 99 percent pure and to remove all except anynegligible trace of the solvent from the lubricating oil fraction.

The raflinate is pumped by means of a pump I through a line 2 in afurnace 3. In passing through the furnace 3 the ramnate is heated to atemperature above the boiling point of the solvent and most of thesolvent is vaporized. The

heated raflinate is passed through a line 4 to an intermediate portionof a bubble tower 5. The bubble tower is provided with a plurality ofbell caps and over-flow pipes according to the usual construction. Theunvaporized portion of' the raflinate flows downwardly through thestripping section of the bubble tower. As the rafiinate flows rdownwardly through the bubble tower more and more of the solventremaining in the ramnateis vaporized by the rising vapors so that thefinal over-flow which is caught upon a pan 6 is substantially free ofsolvent.

The over-flow is delivered from the pan 6 through a line In to anaccumulator II. An intermediate stripping agent is introduced into theaccumulator ll through a line l2. The intermediate stripping agent maycomprise a. narrow petroleum fraction haw'ng a boiling range of apagentis withdrawn through a line 24 to a suitable proximately 450 to 550 F.,and constitutes an intermediate boiling fraction. The intermediateboiling fraction or stripping agent and the overflow from pan 6constitute a mixture which is pumped by a pump I3 through a line it intothe radiant section of the furnace 3 where the mixture is heated to atemperature above the boiling point of the stripping agent whereby themajor portion of the stripping agent is vaporized and a negligibleamount of the high boiling raflinate fraction is vaporized. The partlyvaporized discharge from line H is released into the bubble tower v5below the pan '6 whereby the vapors of the stripping agent rise upwardlythrough the bubble tower and function to strip the low boiling compoundfrom the feed plate over-flow. The bottom reboiling gives a source ofsubstantially solvent free vapors in thelower portion'oi the bubbletower at temperatures not in excess of approximately 600 F; atatmospheric pressure. This temperature will not injure the lubricatingoil traction.

The liquid which accumulates in the bottom of the bubble tower consistssubstantially of the high boiling raflinate fraction with a small amountoi! the stripping agent and a negligible trace of the solvent or lowboiling compound. This liquid is removed from the bubble tower at atemperature of approximately 600 F. and may contain a negligible amountof the solvent and perhaps 10 percent of compounds boiling in the rangeof the intermediate agent. This liquid is removed through a line I! to astripper iii in which substantially all of the residual stripping agentis stripped out by steam which is introduced 35 through a line IS. Theover-head vapors from the stripper l8 are withdrawn through a line 20 toa condenser 2 I. The condensate is introduced into a separating drum 22from which water is withdrawn through a line 23 while the strippingplace of storage, not shown. A vent line 25 balances the separator tothe atmosphere or to a gas collecting system. Instead of stripping thelight ends from the bottoms which are withdrawn from tower5 through lineI! they may be recovered as an over-head out upon the vacuum rerunningof the lubricating oil fraction for finished oils.

The solvent or low boiling compound is withdrawn over-head from thebubble tower through a line 21 to a condenser 28. The condensed solventis delivered to a container 29'. A portion of the condensed solvent isreturned through a line 30 to the upper portion of the bubble tower tofunction as a refluxingagent. The remainder of the condensate iswithdrawn through a line ll to a place of storage, not shown. A ventline 26 balances the tower to the atmosphere or to a noncondensablecollecting system by which the tower pressure is regulated.

An example of low and high boiling materials to be separated accordingto the present invention isthe raffinate obtained in treatinglubricating oils with undiluted phenol. The intermediate boilingsubstance may be in this case a pctroleum fraction boiling between-150to 550 F. When it is desired to separate SO: from a heavy petroleum oilobtained after extraction with liquid S02, the intermediate boilingsubstance may-be either a naphtha boiling between 300 and 400 F. or itmay be benzol or toluol. The solvent dewaxing of lubricating or cylinderoils also leads to solutions of one or more low boiling substances inthe heavy oil. Thus, for example, the dewaxing may be carried out with abenzol acetone mixture in which case the light solvent of benzol andacetone is to be separated from the dewaxed oil. A heavy naphtha or alight gas oil may be used in this case as intermediate boilingsubstance. The same principle may be applied also to cases in which thehigh boiling material is a compound having a single boiling point.

while the invention has been described as applied in the treatment ofrailinate from a solvent extraction treatment or dewaxing of lubricatingoil distillate, it will be understood that it is intended to similarlyseparate compounds from any source having diiferentboiling points. Theprocess is applicable to the separation of pure compounds each having asingle boiling point. It is applicable also to a solution of a purecompound and a fraction having a boiling range such that the boilingpoint of the pure compound lies outside of the boiling range of thefraction. The stripping agent can be a pure compound having a boilingpoint intermediate the boiling points of the relatively low and highboiling compounds. Similarly the stripping agent can be a materialhaving a boiling range which falls within the temperature gap betweenthe final boiling point of the overhead product and the initial boilingpoint of the bottoms product. Preferably the boiling point or boilingrange of the stripping agent lies below and it preferably does notover-lap or include the boiling point or range of the high boilingcompound and it similarly lies above and preferably does not overlap orinclude the boiling point or range of the low boiling compound. Thestripping agent is usually so chosen that its presence in the bottomsproduct is not un desirable and/or so that it can be satisfactorilystripped out in the bottoms product in the usual manner. I

By the process described the compounds are separated from each other byfractionation with a high degree of heat economy The latent heatimparted to the stripping agent does work in vaporizing the low boilingcomponent. The lowering of the temperature is accomplished by reason ofsome of the stripping agent dissolving in the bottoms product and thusraising its vapor pressure. The intermediate agent while not affectingthe temperature at the top of a bubble tower lowers the temperaturesthroughout the lower or stripping section of the bubble tower. Theeffective fractionating pressure is lowered where the totalfractionating pressure is atmospheric or is below or above atmospheric.Consequently any danger of undesirable deterioration or loss of qualityof one of the compounds is minimized. By way of example such pressuresas approximately 12 to 400 pounds per square inch may be employed.

Various changes may be made within the scope of the appended claims inwhich it is desired to claim all novelty inherent in the invention asbroadly as the prior art permits.

I claim:

1. The method of separating a relatively high and a low boiling materialfrom a solution thereof which comprises heating the solution above theboiling point of the lower boiling material, passing the heated solutionthrough a fractionating zone, withdrawing the unvaporized fractions fromthe fractionating zone and mixing them with a substance having a boilingpoint between the boiling points of the materials, heating the mixtureabove the boiling point of the substance, injecting the heated mixtureinto an accumulating zone below the lower portion of the frac- Itionating zone whereby vapors of the substance rising through thefractionating zone strip the lower boiling material from the higherboiling material, removing vapors of the substance and lower boilingmaterial overhead from the fractionating zone and withdrawing theunvaporized bottoms and substance from the bottom of the accumulatingzone.

2. The method of separating a relatively'high and a low boiling materialfrom a solution thereof according to claim 1 in which the process iscarried out under an absolute pressure between 12 pounds per square inchand 400 pounds per square inch.

3. The method of separating a relatively high and a low boiling materialfrom a solution thereof according to claim 1 in which the two materialsof the solution and the intermediate boiling substance comprise threepure compounds, each having a definite boiling point.

4. The method ofseparating a relatively high and a low boiling materialfrom a solution thereof according to claim 1 in which the two materialsof the solution and the intermediate boiling substance comprise threefractions, each having a boiling range.

5. The method of separating a relatively high and a low boiling materialfrom a solution thereof according to claim 1 in which the two materialsof the solution and the intermediate boiling substance comprise a purecompound and two petroleum fractions.

6'. The method of separating a relatively high and a low boilingmaterial from a solution thereof according to claim 1 in which the twomaterials of the solution and the intermediate boiling substancecomprise a petroleum fraction and two pure compounds.

7. The method of separating relatively high and low boiling materialsfrom a solution thereof according to claim 1, in which one of thematerials is a pure compound and has a given boilin point and the othermaterial has .a boiling range, and in which the boiling points of thesubstance and the materials do not over-lap. 8. The method of separatingrelatively high and low boiling materials from a solution thereofaccording to claim 1 in which the boiling ranges of the substance andone of the materials overlap. I

9. The method of separating a relatively high and a low boiling fractionfrom a solution thereof, which comprises heating the mixture above theboiling range of the lower boiling fraction,

passing the heated mixture through a fractionating zone, withdrawing theunvaporized fractions from the fractionating zone and mixing them with asubstance having a boiling range between the boiling ranges of thefractions, heating the mixture above the boiling range of the substance,injecting the heated mixture into an accumulating zone below the lowerportion of the fractionating zone whereby vapors of the substance risingthrough the fractionating zone strip the lower boiling fraction from thehigh boiling fraction,

removing vapors of the substance and lower boil:

ing fraction over-head from the fractionating zone, and withdrawing theunvaporized bottoms and substance from the bottom of the accumulatingzone and stripping the substance from the high boiling fraction.

10. The method of separating a relatively high and a low boilingmaterial from a solution thereof according to claim 9 in which there isa temperature gap between the adjacent limits of the boiling ranges ofany pair of the three fractions.

11. The method of separating a relatively high and a relatively lowboiling material from a solution thereof, which comprises heating thesolution above the boiling point of the lower boiling material, passingthe heated solution through a fractionating zone, withdrawing theunvaporized fractions from the fractionating zone and mixing them with asubstance having a boiling point between the boiling points of thematerials, heating the mixture above the boiling point-of the substance,passing vapors from the heated mixture through the fractionating zonewhereby vapors of the substance rising through the fractionating zonestrip the lower boiling material from the higher boiling material,removing vapors of the lower boiling material overhead from thefractionating zone, and withdrawing the unvaporized bottoms of higherboiling material and substance from the fractionating zone.

12. The method according to claim 11 in which the unvaporized bottomswithdrawn from the fractionating zone is passed through a stripping zonein which the substance is separated from the high boiling material.

1 DANIEL E. STINES.

